New Paper “Impacts Of Land Use Land Cover Change On Climate And Future Research Priorities” By Mahmood Et Al 2009

We have a new multi-authored paper that has been accepted.  This paper illustrates the breadth and diversity of scientists who have concluded that land use/land cover change is a first order climate forcing.

The paper is

Mahmood, R., R.A. Pielke Sr., K.G. Hubbard, D. Niyogi, G. Bonan, P. Lawrence, B. Baker, R. McNider, C. McAlpine, A. Etter, S. Gameda, B. Qian, A. Carleton, A. Beltran-Przekurat, T. Chase, A.I. Quintanar, J.O. Adegoke, S. Vezhapparambu, G. Conner, S. Asefi, E. Sertel, D.R. Legates, Y. Wu, R. Hale, O.W. Frauenfeld, A. Watts, M. Shepherd, C. Mitra, V.G. Anantharaj, S. Fall,R. Lund, A. Nordfelt, P. Blanken, J. Du, H.-I. Chang, R. Leeper, U.S. Nair, S. Dobler, R. Deo, and J. Syktus, 2009: Impacts of land use land cover change on climate and future research priorities. Bull. Amer. Meteor. Soc., accepted.

The paper starts with the text

“Human activities have modified the environment for thousands of years. Significant population increase, migration, and accelerated socio-economic activities have intensified these environmental changes over the last several centuries. The climate impacts of these changes have been found in local, regional, and global trends in modern atmospheric temperature records and other relevant climatic indicators.”

In our conclusions, we write

“It is the regional responses, not a global average, that produce drought, floods and other societally important climate impacts.”

as well as make the following recommendations

“we recommend, as a start, to assess three new climate metrics:

1. The magnitude of the spatial redistribution of land surface latent and sensible heating (e.g., see Chase et al. 2000; Pielke et al. 2002). The change in these fluxes into the atmosphere will result in the alteration of a wide variety of climate variables including the locations of major weather features. For example, Takata et al. (2009) demonstrated the major effect of land use change during the period 1700-1850 on the Asian monsoon. As land cover change accelerated after 1850 and continues into the future, LULCC promises to continue to alter the surface pattern of sensible and latent heat input to the atmosphere.

2. The magnitude of the spatial redistribution of precipitation and moisture convergence (e.g., Pielke and Chase 2003). In response to LULCC, the boundaries of regions of wet and dry climates can change, thereby affecting the likelihood for floods and drought. This redistribution can occur not only from the alterations in the patterns of surface sensible and latent heat, but also due to changes in surface albedo and aerodynamic roughness (e.g., see Pitman et al. 2004; Nair et al. 2007).

3. The normalized gradient of regional radiative heating changes. Since it is the horizontal gradient of layer-averaged temperatures that force wind circulations, the alteration in these temperatures from any human climate forcing will necessarily alter these circulations. In the evaluation of the human climate effect from aerosols, for example, Matsui and Pielke (2006) found that, in terms of the gradient of atmospheric radiative heating, the role of human inputs was 60 times greater than the role of the human increase in the well-mixed greenhouse gases. Thus, this aerosol effect has a much more significant role on the climate than is inferred when using global average metrics. We anticipate a similar large effect from LULCC. Feddema et al. (2005), for example, have shown that global averages mask the impacts on regional temperature and precipitation changes. The above climate metrics can be monitored using observed data within model calculations such as completed by Matsui and Pielke (2006) for aerosols, as well as by using reanalyses products, such as performed by Chase et al (2000) with respect to the spatial pattern of lower tropospheric heating and cooling. They should also be calculated as part of future IPCC and other climate assessment multi-decadal climate model simulations.”

We also write

“With respect to surface air temperatures, for example, there needs to be an improved quantification of the biases and uncertainties in multi-decadal temperature trends, which remain inadequately evaluated in assessment reports such as from the Climate Change Science Program (CCSP 2006). We also recommend that independent committees (perhaps sponsored by the National Science Foundation) conduct these assessments.”

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